On Thu, Feb 22, 2024 at 4:04 PM Yu Kuai <yukuai1@xxxxxxxxxxxxxxx> wrote:
>
> From: Yu Kuai <yukuai3@xxxxxxxxxx>
>
> read_balance() is hard to understand because there are too many status
> and branches, and it's overlong.
>
> This patch factor out the case to read the slow rdev from
> read_balance(), there are no functional changes.
>
> Co-developed-by: Paul Luse <paul.e.luse@xxxxxxxxxxxxxxx>
> Signed-off-by: Paul Luse <paul.e.luse@xxxxxxxxxxxxxxx>
> Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
> ---
> drivers/md/raid1.c | 69 ++++++++++++++++++++++++++++++++++------------
> 1 file changed, 52 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
> index 08c45ca55a7e..bc2f8fcbe5b3 100644
> --- a/drivers/md/raid1.c
> +++ b/drivers/md/raid1.c
> @@ -620,6 +620,53 @@ static int choose_first_rdev(struct r1conf *conf, struct r1bio *r1_bio,
> return -1;
> }
>
> +static int choose_slow_rdev(struct r1conf *conf, struct r1bio *r1_bio,
> + int *max_sectors)
> +{
> + sector_t this_sector = r1_bio->sector;
> + int bb_disk = -1;
> + int bb_read_len = 0;
> + int disk;
> +
> + for (disk = 0 ; disk < conf->raid_disks * 2 ; disk++) {
> + struct md_rdev *rdev;
> + int len;
> + int read_len;
> +
> + if (r1_bio->bios[disk] == IO_BLOCKED)
> + continue;
> +
> + rdev = conf->mirrors[disk].rdev;
> + if (!rdev || test_bit(Faulty, &rdev->flags) ||
> + !test_bit(WriteMostly, &rdev->flags))
> + continue;
> +
> + /* there are no bad blocks, we can use this disk */
> + len = r1_bio->sectors;
> + read_len = raid1_check_read_range(rdev, this_sector, &len);
> + if (read_len == r1_bio->sectors) {
> + update_read_sectors(conf, disk, this_sector, read_len);
> + return disk;
> + }
> +
> + /*
> + * there are partial bad blocks, choose the rdev with largest
> + * read length.
> + */
> + if (read_len > bb_read_len) {
> + bb_disk = disk;
> + bb_read_len = read_len;
> + }
> + }
> +
> + if (bb_disk != -1) {
> + *max_sectors = bb_read_len;
> + update_read_sectors(conf, bb_disk, this_sector, bb_read_len);
> + }
> +
> + return bb_disk;
> +}
> +
> /*
> * This routine returns the disk from which the requested read should
> * be done. There is a per-array 'next expected sequential IO' sector
> @@ -672,23 +719,8 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
> if (!test_bit(In_sync, &rdev->flags) &&
> rdev->recovery_offset < this_sector + sectors)
> continue;
> - if (test_bit(WriteMostly, &rdev->flags)) {
> - /* Don't balance among write-mostly, just
> - * use the first as a last resort */
> - if (best_dist_disk < 0) {
> - if (is_badblock(rdev, this_sector, sectors,
> - &first_bad, &bad_sectors)) {
> - if (first_bad <= this_sector)
> - /* Cannot use this */
> - continue;
> - best_good_sectors = first_bad - this_sector;
> - } else
> - best_good_sectors = sectors;
> - best_dist_disk = disk;
> - best_pending_disk = disk;
> - }
> + if (test_bit(WriteMostly, &rdev->flags))
> continue;
> - }
> /* This is a reasonable device to use. It might
> * even be best.
> */
> @@ -799,7 +831,10 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
> }
> *max_sectors = sectors;
>
> - return best_disk;
> + if (best_disk >= 0)
> + return best_disk;
> +
> + return choose_slow_rdev(conf, r1_bio, max_sectors);
> }
>
> static void wake_up_barrier(struct r1conf *conf)
> --
> 2.39.2
>
>
This patch looks good to me.
Reviewed-by: Xiao Ni <xni@xxxxxxxxxx>
